This research project concerns the study of enzyme reaction mechanisms, protein structure-function relationships, protein-protein interactions, protein biosynthesis, and mechanisms of long range biological electron transfer. The proposed studies focus on the tryptophan tryptophylquinone [TTQ] bearing enzyme methylamine dehydrogenase [MADH], and the electron transfer complex it forms with the type I copper protein amicyanin and cytochrome c-551i. MauG, a novel di-heme protein that is required for TTQ biosynthesis is also under study. Elucidation of factors which influence the specific protein-protein interactions that are required for efficient interprotein electron transfer is providing insight into the process of protein-protein recognition that is common to a wide range of biologic phenomena. Characterization of the catalytic reaction mechanisms of MADH is allowing us to better understand how enzymes, in general, catalyze reactions. Definition of the mechanisms of long range intermolecular electron transfer will allow us to better understand the fundamental processes of respiration and intermediary metabolism at the molecular level. Description of the mechanism of biosynthesis of TTQ will help us understand how amino acid residues may acquire new functions as a result of posttranslational modification. Characterization of the structure and function of MauG will enhance our understanding of the role of heme proteins in biological oxygen activation reactions. The results to be obtained from these proposed studies will also allow us to better understand the factors which influence the oxidation and oxygenation of amino acid residues in proteins, a medically and biologically important process which remains poorly understood.